Liquid usage monitoring

ABSTRACT

A method and apparatus for monitoring usage of liquids of high value or sensitive nature which are applied in repeated small controlled volumes are provided by monitoring and recording parameters including the number of applications, purging, priming and cleaning steps and the usage of liquid supply and circulation pumps. The monitored parameters present a record of the total liquid usage. The recorded usage of the liquid pumps can be cross-checked with the volumes indicated by the other parameters so as to highlight any disagreement between the respective indications of total liquid volumes employed, thereby alerting the user to possible operating problems and permitting prompt remedial action to be taken.

FIELD OF THE INVENTION

This invention relates to monitoring liquid usage. It is particularlyconcerned with monitoring to a high level of precision the usage ofliquids of high value or potentially sensitive nature.

BACKGROUND OF THE INVENTION

There is a wide variety of processes and procedures in which the levelof usage of a liquid material needs to be monitored. In its simplestform the need is to ensure the presence of sufficient liquid to performthe required duty, for example in a storage vessel such as a vehiclefuel tank. In such applications a float or other liquid level indicatormonitors the liquid volume, albeit without great precision, and maytrigger a signal to indicate when the volume falls to a low level.

Somewhat more precise monitoring has been provided by flow meters, forexample including a rotor or turbine in a liquid conduit, which can belinked directly or indirectly to signalling and control elements. Thenumber of rotations are counted and used to generate a signal indicatingthe volume flow. Such rotary meters have been well developed in thefield of fuel pumps, especially for vehicle filling stations, andprovide a sufficiently precise measurement for supply of relatively highliquid volumes. Various features have been adopted for the electricalcontrol circuits of such pumps. For example U.S. Pat. No. 3,990,607relates to a relay-controlled circuit of a gasoline pump in whichmomentary closure of a key-operated switch is required before normaloperation of the pump can be reinstated after a dispensing operation.

For certain liquids a higher level of monitoring precision is requiredthan for such commodities as gasoline. These liquids includepharmaceuticals, certain chemical treatment agents, radioactive or toxicmaterials, and special purpose materials, for example special purposeprinting inks as may be used in inkjet printers. In general suchmaterials are applied in dosed quantities, i.e. a small controlledvolume is applied repeatedly from a source container which is refilledor replaced as the liquid is consumed.

In the field of inkjet printing it is customary to monitor the remainingvolumes of ink in supply cartridges so as to warn the user of when tofit a replacement cartridge. In its simplest form the monitoring isprovided by a small inspection window in the cartridge. Moresophisticated monitoring has been proposed in certain instances. U.S.Pat. No. 6,045,206 discloses a method of operating an inkjet printercomprising the steps of using a maintenance algorithm to control timingof a maintenance action, keeping a historical log of an operatingcharacteristic of the printer over a period of time, and changing themaintenance algorithm for subsequent use by the printer based upon thehistorical log.

A complete record of the usage of liquid materials requires not just anawareness of operating characteristics and of volumes directly applied,but also any wastage resulting from such steps as priming, purging andcleaning the apparatus used in the application.

SUMMARY OF THE INVENTION

According to the invention there is provided a method of monitoring theusage of a liquid applied in repeated small controlled volumes fromapplication apparatus which provides for purging, priming and cleaningsteps, which apparatus includes one or more liquid pumps for supply orcirculation of liquid and in which method parameters of usage aremonitored and recorded in transmittable form, the monitored parametersincluding the number of applications, the number of purging, priming andcleaning steps and the periods of usage of each liquid pump.

The invention further provides apparatus for monitoring the usage of aliquid applied in repeated small controlled volumes, which apparatusprovides for purging, priming and cleaning steps and includes one ormore liquid pumps for supply or circulation of liquid, in whichparameters of usage are monitored and recorded in transmittable form,the monitored parameters including the number of applications, thenumber of purging, priming and cleaning steps and the periods of usageof each liquid pump.

The objective is to ensure that the monitored parameters represent asubstantially complete record of the liquid usage. Given that thetypical liquid volume used in each individual application is known,recordal of the number of applications shows the volumes directly usedin the application. The volumes used indirectly, and which may beregarded as waste, are shown by the total of any volumes used inpurging, priming and cleaning the apparatus. These waste volumes caneither be measured directly, for example by measuring an increase inweight of an absorbent material used in cleaning the apparatus, orindirectly by counting the number of purging, priming and cleaning stepsand multiplying these by the volumes routinely consumed in these steps.

A particular advantage of the invention is that recordal of the usage ofliquid pumps, whose liquid handling capacity can also be determined,provides an indication of total volumes employed, which can becross-checked with the volumes indicated by the other parameters. Anydisagreement between the respective indications of total liquid volumesemployed alerts the user to possible operating problems, for exampleerrors or malfunctioning of the apparatus, and permits prompt remedialaction to be taken.

In order to increase the level of precision of the usage monitoring, orto provide additional cross-checks on the level of usage, it may also bedesirable to monitor other parameters, including for example the numberof on and off operations of switches and control valves in theapparatus.

The volumes and/or associated actions of the respective elements arepreferably monitored and controlled by one or more microprocessors, forexample a programmable logic controller. The microprocessors can behoused within or alongside the application apparatus, but can be locatedremote from it. In one convenient arrangement one microprocessor formspart of the apparatus as such and another microprocessor is locatedremotely. A remote location is beneficial in permitting a reduction inon-site inspection time by local personnel and in permitting severalapplication stations to be monitored and controlled from a single point.The microprocessors can be configured to receive data electronically bysuch transmission routes as a direct wiring connection, dedicatedtelephone line, radio link or internet link.

DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of liquid usage monitoring system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one convenient embodiment of the invention the liquid is suppliedfrom a replaceable container holding a defined initial liquid volume.Because the starting volume in the container and the precise consumptionare both known, an operator can determine when the container contentsare about to run out and can arrange for a replacement. The precisionalso allows for substantially complete use to be made of an individualcontainer contents, thereby maximizing the period between containerreplacements and removing the possibility of significant volumes beingreturned with the spent container.

The invention is applicable to all types of process liquids that demandspecial attention. They may be used alone or in some instances maycontain constituents in solution or in suspension. Indeed it may be thedissolved or suspended content that gives the liquid the unusualcharacteristics that demand its carefully monitored usage. For example,the liquids or their constituents may be expensive and therefore usedsparingly for reasons of economy. It is therefore desirable to use onlyas much of such materials as is strictly necessary for a given duty andto dispose effectively of any material not directly employed in theprocess.

In the case of sensitive materials, especially if they are of aperishable nature, replacement may be necessary before all the containercontents have been used. This can be achieved by recording a “use-by”date for the container and checking before a given application that theliquid is prior to that date. The check can be provided by programming amicroprocessor to alert the operator to the approach of the expirationdate. The microprocessor can also be programmed to stop supply of theliquid at the expiration date. The invention has the further benefit ofpermitting such checks and control of materials that may havepotentially harmful characteristics.

It may be desirable to return the spent container for refilling by anapproved supplier. This ensures that the replacement liquid is of anapproved quality and in the precise filled volume desirable forsuccessful monitoring. The container is preferably sealed after approvedrefilling so that tampering with the contents is prevented. Sealing isespecially appropriate for handling sensitive or hazardous material inthat it protects the user from coming into contact with the material.

In another embodiment of the invention the liquid container may form anintegral part of the apparatus employing the liquid. In this embodiment,both the container and the portion of the apparatus of which it forms apart must be returned to the approved supplier for replenishment of theliquid. The returnable unit may desirably be sealed to protect the userfrom coming into contact with the liquid contents.

For some printing duties, especially those using sensitive inks, the keyparameters to be monitored are the number of images applied and a recordof the movements of the system, notably when it was returned to asupplier for refilling. These provide the operator with useful data onthe number of articles produced and marked and the frequency with whichthe system must be returned for refilling.

Optionally the monitoring of the transmitted records is effectedautomatically. The microprocessor can be configured to transmit warningsignals, for example when a container is about to run out of liquid.

Individual containers can be marked with one or more serial numbers orcodes. This is helpful in identifying the specific container and itscontents. In one preferred embodiment of the invention the serial numberis recorded on the container in such a way that it can also betransmitted to the microprocessor. This allows the microprocessor toshow which container is in place in the application apparatus andfurther facilitates remote control of when a replacement container willneed to be provided. If desired the microprocessor can be programmed soas to permit operation of the apparatus only if it recognizes thecontainer as having an approved serial number, thereby preventinginstallation in the apparatus of an unapproved container and thus of useof unapproved operating liquid. The recognition may be, for example, bybar-code or radio frequency identification (RFID) tag.

It may additionally be desirable for the microprocessor to demand apassword from the operator before opening up the apparatus to thereplacement container. This helps to ensure that only appropriatelyqualified personnel can install the replacements. This option isespecially relevant for use of highly sensitive liquids, for examplepotentially hazardous (such as radioactive) materials.

In the case of particularly sensitive materials it may be desirable toequip the container, and any apparatus of which it forms a part, with ahoming device which transmits a signal to indicate its whereabouts. Thehoming device can be programmed to emit or transmit a warning signal,which again can be an RFID signal, if the container is moved away fromknown acceptable locations.

The present invention is further described with reference to theaccompanying figure which is a schematic side view, partly in section,of the print head of an ink-jet printer fitted with one version ofmonitoring system according to the invention. The invention is relevantto this application because of the unusual and sensitive nature ofcertain inks used in the printing process. It is emphasized that theinvention is not limited to this application or to the specific versionof system described and that not all of the components illustrated inthis version represent essential features of the invention.

By way of example it may be noted that the ink used in the inkjetprinter may contain a special marker selected from one or more dyes orsolid particulate materials. The marker may be of a type that imparts tothe deposited image a coloration which is visible in daylight orconventional artificial lighting, or may have no marked colour indaylight or conventional artificial lighting but reveal their colourunder special lighting, for example from an ultra-violet or LED source.Alternatively the marker may be a pigment or additive which reveals itspresence under the application of magnetic, electronic or spectroscopicmeans.

Examples of types of pigments used in inkjet printer inks are metallicflakes, inorganic materials comprising ferrites and other metal oxides,including oxides of transition and rare earth metals; organo-metalliccomplexes; and organic materials, including high molecular weightaromatic compounds such as anthraquinones, aryl amides andquinacridones. Specific examples of commonly used pigments includemagnetite, barium ferrite, strontium ferrite, iron oxide, titaniumdioxide, copper phthalocyanine and carbon black.

A wide variety of images can be applied by an inkjet printer, includinglettering, numerals, figures, photographs, pictures, logos, identifyingmarks, “sell-by” or “use by” dates as mentioned above, batch numbers,address details and general text. The required degree of precision ofthe image depends on the duty and the sophistication of the print head.

The system illustrated in the figure is intended for industrialapplication of coding details, for example batch numbers, to articles ona production line. It includes a print head 10, of a type marketed as aTrident Ultrajet”, attached to the front of a housing 20. The print head10 has multiple internal capillary channels with ink ejection nozzles11. Within the print head 10 each capillary has an associatedpiezoelectric element controlled by energy pulses to eject ink dropletswhich collectively form the desired image.

A primary reservoir 14 which serves as the main container for ink has aninlet tube 16 and outlet tube 18 and a level sensor 15. The inlet tube16 includes a flow meter 12, to monitor the rate of ink transfer, and anon-off valve 13.

An ink feed pump 17 in the outlet tube 18 conveys ink through an in-linestatic mixer 19 to ensure complete dispersion of any ink solids. Fromthe mixer 19 the tube 18 continues to a secondary reservoir 22 locatedat a higher level than the primary reservoir 14.

The secondary reservoir 22 has an ink level sensor 23, which with thepump 17 maintains the volume of ink in the secondary reservoir 22 at aconstant level. An outlet line 25 from the reservoir 22 passes to apriming pump 30 and a flow meter 31.

The print head 10 carries a shaped capping arm 36 rotatably disposed ona shaft 38 and a spring-loaded padded capping plate 40 to close and capthe nozzles 11.

A wiper blade 39 is located at indicated position 39 and extends acrossthe width of the body portion of the print head 10. The wiper blade 39is mounted on a lever frame 41 comprising interconnected levers moved byan electrically driven wheel 42. One set of levers on the frame 41 isvisible at the near side of the print head body portion 10 as viewed inthe figure: equivalent levers are located at the far side. An absorbentpad 45 is located beneath the nozzles 11 to receive ink flicked awayfrom the nozzles 11 by the action of the wiper blade 39 and to contactthe wiper blade 39 as it returns to the parked position so as to removeany residual ink from it.

At the start of a printing operation the pump 30 is activated to primethe print head 10 with ink. The relative disposition of the reservoirs14 and 22 is such that because of the height difference ink is siphonedthrough the print head 10, ensuring that the print head 10 receives aconstant flow of ink at a uniform and low ink feed pressure. After theinitial priming, the pump 30 can be switched off, ink circulation beingthen achieved by the siphon effect and the action of the ink feed pump17 alone.

A programmable logic controller 50 is located inside the housing 20 nearthe top and is connected by circuit wiring (indicated by dotted lines52) to the respective elements of the system. The controller 50 has anexternal port 51 to receive a connector from an associated remotecontroller (not shown).

Prior to a print run the print head 10 is at rest as shown in thefigure, with the capping arm 36 holding the capping plate 40 firmlyagainst the nozzles 11. The capping arm 36 is moved away and the drivewheel 42 is then activated to operate the lever frame 41 so as to movethe wiping blade 39 from its parked position to an upper position,slightly above the nozzles 11. The print head 10 is then primed and thenozzles 11 purged by the action of the priming pump 30.

The wiper blade 39 is then brought into operation by continued rotationof the drive wheel 42, causing the frame 41 to draw the wiper blade 39vertically downwards and over the nozzles 11 to remove any ink fromthem. Most of any ink on the head face is flicked away by the wipingaction of the wiper blade 39 and is deposited on the absorbent pad 45.Residual ink is removed from the wiper blade 39 as it contacts theabsorbent pad 45 on its return to the parked position. The volumes ofink removed by the wiper blade 39 are readily taken up by the absorbentpad 45 and are thus effectively removed from the system, being heldwithin the pad 45 such that they cannot result in misuse, for example byan unauthorized party. The pad 45 is replaced by a new pad after aseries of print runs.

With the wiper blade 39 and the blade lever frame 41 back in the parkedposition, the printer is now ready for a print run. At the end of therun the capping arm 36 is returned to the capping position of thefigure.

The controller 50 prevents the wiping action from being initiated if thecapping plate 40 is in position and, vice versa, prevents the cappingarm 36 from being operated if the wiping action is in progress.

The remote controller dictates the image pattern by activating thepiezoelectric elements in the print head 10, for example by sending acontrolled voltage to the print head 10. Thus effectively it monitorsthe number of images applied. Together with the controller 50 it canmonitor these and all other actions associated with the printing: theinitial opening of the on-off valve 13, the capping and uncappingactions of the capping arm 36, purge and priming steps, the wipingaction of the wiper blade 39, the number of activations of the liquidpumps and the length of time for which they are operated, the flow ratesthrough meters 12 and 31, and the levels indicated by the level sensors15 and 23. The controllers can further be programmed to monitor theoccasions on which data is extracted from them. The count of the numberof marks applied is of particular benefit for a production run ofarticles which each receive marks such as batch numbers or sell bydates, since the count provides a ready check on the number of articlesproduced in a given run. Recordal of the monitored data is effected bythe controller 50, which can be interrogated by the remote controller orany other chosen control unit.

The level sensor 15 gives a warning of the ink level in the reservoir 14falling to a point at which the need for refilling is approaching. Italso permits any adjustment of any drift in the residual volumescalculated by the controller 50 from its awareness of the direct andindirect usage of the ink. From its awareness of the rate of usage italso permits a precise estimate of when the ink will run out, and thusof the urgency for refilling.

Refilling can either be effected directly by decanting fresh ink intothe main reservoir 14 or by removing the reservoir 14 or even the entireunit to a filling station. Removal of the reservoir 14 or unit may bethe preferred options for inks of a sensitive or potentially hazardousnature in that the refilling can be conducted by suitably skilled staffunder controlled conditions.

1. A method of monitoring the usage of a liquid applied in repeatedsmall controlled volumes from an application apparatus which providesfor purging, priming and cleaning steps, which apparatus includes atleast one liquid pump (17) for supply or circulation of liquid, saidmethod comprising the steps of: monitoring one or more parameters ofliquid usage; recording the one or more parameters of liquid usage in atransmittable form; wherein the one or more parameters of liquid usageinclude the periods of usage of each liquid pump (17).
 2. A method asclaimed in claim 1, in which the one or more parameters of liquid usagefurther include the number of on and off operations of switches andcontrol valves (13) in the apparatus.
 3. A method as claimed in claim 1,in which the one or more parameters of liquid usage further include (i)the number of applications, and (ii) the number of purging, priming andcleaning steps.
 4. A method as claimed in claim 1, in which the one ormore parameters of liquid usage further include the rate of liquidtransfer through at least one flow meter (12, 31).
 5. A method asclaimed in claim 1, further comprising the step of: cross-checking atotal volume of liquid employed, which is determined from the periods ofusage of each liquid pump (17) and a liquid handling capacity of eachpump (17) with an estimated usage of liquid determined by adding (i) theproduct of multiplying the number of applications by a typical liquidvolume used in each individual application and (ii) the product ofmultiplying the number of purging, priming and cleaning steps by avolume routinely consumed in these steps.
 6. A method as claimed inclaim 1, in which the liquid is supplied from a replaceable containerholding a defined initial liquid volume.
 7. A method as claimed in claim6, in which the container is returned to an approved supplier forrefilling.
 8. A method as claimed in claim 7, in which the container issealed after approved refilling to prevent tampering with its contents.9. A method as claimed in claim 6, in which the container forms anintegral part of the apparatus employing the liquid.
 10. A method asclaimed in claim 1, in which the volumes and/or associated actions ofthe respective elements are monitored and controlled by at least onemicroprocessor.
 11. A method as claimed in claim 10, in which amicroprocessor is housed within the application apparatus.
 12. A methodas claimed in claim 11, in which one microprocessor forms part of theapparatus as such and another microprocessor is located remotely.
 13. Amethod as claimed in claim 12, in which the microprocessors areconfigured to receive data electronically by one or more of a directwiring connection, dedicated telephone line, radio link or internetlink.
 14. A method as claimed in claim 10, in which a microprocessor isconfigured to transmit warning signals.
 15. A method as claimed in claim10, in which a serial number is recorded on one or more liquidcontainers of the application apparatus in such a way that the serialnumber(s) can also be transmitted to the microprocessor.
 16. A method asclaimed in claim 15, in which the microprocessor is programmed so as topermit operation of the apparatus only if it recognizes one or moreliquid containers as having an approved serial number.
 17. A method asclaimed in claim 10, in which the microprocessor is programmed to demanda password before opening up the apparatus to a replacement container.18. A method as claimed in claim 10, in which the microprocessor isprogrammed to alert an operator to the approach of an expiration date ofthe liquid.
 19. A method as claimed in claim 10, in which themicroprocessor is programmed to stop supply of the liquid at theexpiration date of the liquid.
 20. A method as claimed in claim 1, inwhich a homing device associated with one or more liquid containerstransmits a signal to indicate its whereabouts.
 21. Apparatus formonitoring the usage of a liquid applied in repeated small controlledvolumes, said apparatus including: one or more liquid pumps (17) forsupply or circulation of liquid; and at least one microprocessor (50) tomonitor and record in a transmittable form one or more parameters ofliquid usage, wherein the one or more parameters of liquid usage includethe periods of usage of each liquid pump (17).
 22. Apparatus as claimedin claim 21, in which the one or more parameters of liquid usage furtherinclude (i) the number of on and off operations of switches and controlvalves (13) in the apparatus, (ii) the number of applications, (iii) thenumber of purging, priming and cleaning steps, (iv) the rate of liquidtransfer through at least one flow meter (12, 31).
 23. Apparatus asclaimed in claim 21, wherein the apparatus is capable of cross-checkinga total volume of liquid employed, which is determined from the periodsof usage of each liquid pump (17) and a liquid handling capacity of eachpump (17) with an estimated usage of liquid determined by adding (i) theproduct of multiplying the number of applications by a typical liquidvolume used in each individual application and (ii) the product ofmultiplying the number of purging, priming and cleaning steps by avolume routinely consumed in these steps.
 24. Apparatus as claimed inclaim 21, in which one microprocessor forms part of the apparatus andanother microprocessor is located remotely.
 25. Apparatus as claimed inclaim 21, which includes a replaceable container holding a definedinitial liquid volume.
 26. Apparatus as claimed in claim 21, whichincludes a homing device which transmits a signal to indicate itswhereabouts.
 27. An inkjet printer including an apparatus as claimed inclaim 21.